Composite repairing agent for heavy metal contaminated soil and application of composite repairing agent in rice planting

Abstract

The invention provides a composite remediation agent for heavy metal contaminated soil, and relates to the technical field of soil remediation. The composite microbial agent is prepared from the following raw materials in parts by weight: 65-75 parts of a load carrier, 10-15 parts of a composite auxiliary agent and 15-20 parts of a composite microbial agent, the load carrier is prepared from the following components in parts by weight: 35 to 40 parts of rice straw, 35 to 40 parts of oyster shell powder, 10 to 20 parts of hydroxyapatite and 10 to 15 parts of diatomite; the composite auxiliary agent is prepared from the following components in parts by weight: 5 to 10 parts of potassium fulvate and 5 to 15 parts of potassium magnesium silicate; 2-5 parts of zinc selenite, and the balance being water; the complex microbial inoculant is prepared from the following strains: trichoderma harzianum, bacillus thuringiensis, pseudomonas aeruginosa and azotobacter chroococcum; the invention further provides application of the repairing agent in rice planting. According to the scheme provided by the invention, the content of heavy metals in polished rice and soil can be effectively reduced, and meanwhile, the improvement of the rice yield is promoted.

Description

Technical Field

[0001] The present application relates to the technical field of soil remediation, and in particular to a composite remediation agent for heavy metal contaminated soil and its application in rice cultivation. Background Art

[0002] Soil is not only an important part of the ecological environment, but also one of the main natural resources for human survival. Soil has a certain self-purification capacity, but with the rapid development of the world economy, the global population has risen rapidly, and various heavy metals and other pollutants emitted in the process of human production and life have seriously exceeded the self-purification capacity of the soil itself, resulting in the degradation of farmland soil quality and weakening of functions, causing a decrease in crop yield and quality. Soil heavy metals generally refer to the pollution of farmland soil by heavy metals such as cadmium Cd, lead Pb, chromium Cr, mercury Hg, arsenic As, copper Cu, and zinc Zn, among which Cd pollution is the most serious. The biological toxicity of Cd is particularly significant, second only to mercury. It is not easy to degrade in nature and is easily absorbed and accumulated by plants, affecting the yield and quality of crops. Long-term consumption of foods with high cadmium content will cause serious damage to the physiological functions of the human body.

[0003] In 2014, the Ministry of Environmental Protection and other departments discovered in a nationwide survey on contaminated soil that the problem of excessive heavy metal content in rice in some parts of southern my country's rice-growing areas is becoming increasingly prominent, posing a serious threat to rice quality safety. Summary of the invention

[0004] The purpose of this application is to provide a composite remediation agent for heavy metal soil pollution and its application in rice cultivation to solve at least one of the above-mentioned technical problems.

[0005] In order to achieve the above technical objectives, the present application provides a composite repair agent for heavy metal soil pollution and its application in rice planting. In the first aspect, the present application provides a composite repair agent for heavy metal soil pollution, which is composed of the following raw materials in parts by weight: 65-75 parts of a load carrier, 10-15 parts of a composite auxiliary agent and 15-20 parts of a composite bacterial agent;

[0006] The load carrier is composed of the following parts by weight: 35-40 parts of rice straw, 35-40 parts of oyster shell powder, 10-20 parts of hydroxyapatite, and 10-15 parts of diatomaceous earth;

[0007] The composite auxiliary agent is composed of the following parts by weight: 5-10 parts of potassium humate, 5-15 parts of potassium magnesium silicate, 2-5 parts of zinc selenite, and the rest is water;

[0008] The composite bacterial agent is composed of the following bacterial species: Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa and Nitrogen-fixing Bacterium chlororaphis.

[0009] Preferably, the load carrier is prepared by the following method:

[0010] A1. The corn stalks are crushed and mixed with hydroxyapatite, and then calcined for 30-35 min at 300° C. in a nitrogen atmosphere, and then heated to 550° C. for 1 h, and then heated to 700° C. for 2.5 h, and then cooled to obtain a first base material; the oyster shell powder is washed and crushed into small pieces, and then dried in a high-pressure tank, taken out and squeezed into powder, sieved, and then water is added to form a second base material;

[0011] A2. Mix the first base material, the second base material and diatomaceous earth, stir at 25-30°C and 400-450 r / min for 30-35 min; heat to 50-55°C and stir for 1 h, then vacuum filter and collect the precipitate, and dry to obtain the loaded carrier.

[0012] Preferably, the composite bacterial agent is prepared by the following method:

[0013] B1, culturing Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chrysogenum in liquid seed culture medium at 25°C, 30°C, 37°C, and 28°C for 24 h, respectively;

[0014] B2. The cultured bacterial liquid was inoculated into LB liquid culture medium at 10% inoculation rate, and cultured under shaking conditions of 25°C, 30°C, 37°C, and 28°C until the bacterial concentration reached OD600≈2.5. The mixture was evenly mixed at any mass ratio to obtain a composite bacterial agent.

[0015] Preferably, in step B2, the Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chlororaphis are mixed in a ratio of 2:1:2:2.

[0016] Preferably, the Trichoderma harzianum is purchased from China General Microbiological Culture Collection Center with a collection number of CGMCC-3.12840;

[0017] The Bacillus thuringiensis was purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-1.8790;

[0018] The Pseudomonas aeruginosa was purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-1.10452;

[0019] The brown spherical nitrogen-fixing bacteria were purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-1.492.

[0020] Preferably, the composite repair agent is prepared by the following method:

[0021] S1, the carrier is mixed with the culture medium and then sterilized at high temperature, cooled to room temperature, inoculated with 10% of the composite bacterial agent, and cultured at 28-30° C. for 24 hours to obtain a first intermediate solution;

[0022] S2. Dissolve potassium magnesium silicate and zinc selenite in the silicon solution to obtain a second intermediate solution. Mix the first intermediate solution, the second intermediate solution and potassium humate, stir and filter, and dry the precipitate to obtain the composite repair agent.

[0023] In a second aspect, the present application provides an application of any of the above-mentioned composite repair agents in rice planting, wherein the application method comprises the following steps:

[0024] C1. Before transplanting rice seedlings, the paddy field is ploughed and the composite repair agent is applied at a dosage of 5-10 kg / mu. Water is added to cover the soil surface with a 2-3 cm water layer. After standing for 3 days, the field is ploughed again, and then the rice seedlings are transplanted after standing for another 5 days.

[0025] C2. After the rice enters the tillering stage, spray the compound adjuvant at 0.5-1L / mu to cover the soil surface with a water layer of 2-3.5cm;

[0026] C3. After the rice enters the booting stage, apply the composite repair agent at a rate of 0.5-1kg / mu, so that the soil surface is covered with a 3.5-5cm layer of water.

[0027] C4. Keep the soil surface covered with 2-3cm of water during the flowering, filling and milky stages of rice until the rice enters the waxy stage and is harvested.

[0028] Preferably, in step C1, the application amount of the composite repair agent is 8 kg / mu.

[0029] Preferably, the rice variety is Juliangyou 751.

[0030] Preferably, the application is to reduce the cadmium content in rice.

[0031] Compared with the prior art, this application has at least the following technical effects:

[0032] (1) The composite repair agent is composed of three major components, which work synergistically with each other. The load carrier and the composite bacterial agent work together to form a composite bacterial agent. The composite bacterial agent can achieve the absorption and fixation of free heavy metal ions, and the load carrier can provide a stable adsorption point for the composite bacterial agent to avoid the rapid loss of core bacteria, so as to achieve long-term soil remediation. The composite auxiliary agent cooperates to provide trace elements, forms a synergistic effect with the soil body, and provides a good basic environment for the growth of microorganisms.

[0033] (2) The raw material source is green and environmentally friendly. The load carrier is mainly composed of some agricultural and aquatic waste materials, such as rice straw and oyster shell powder. Using waste materials as the main raw material of the load carrier can make full use of waste resources and is also more green and environmentally friendly;

[0034] (3) The load carrier in this scheme further includes hydroxyapatite, which is easy to react with heavy metal ions to form a complex, thereby showing a relatively excellent heavy metal adsorption capacity, and improving the load carrier's own heavy metal adsorption capacity. At the same time, the metabolites secreted by the composite bacterial agent attached to the load carrier can also react with heavy metal ions to a certain extent, thereby achieving the adsorption of heavy metal ions; further, the rich phosphorus element can also provide assistance for plant growth, which is beneficial to reduce diseases and increase rice yields;

[0035] (4) Diatomaceous earth has a large number of pores and specific surface area, which makes it have a strong adsorption capacity. The silanol (SiOH) on the surface of diatomaceous earth can be hydrolyzed in aqueous solution to form charged siloxy groups. These groups undergo ion exchange and surface complexation reactions with heavy metal ions. At the same time, the pore structure on its surface allows heavy metal ions to be physically adsorbed on its surface. Furthermore, diatomaceous earth and the various strains in the composite bacterial agent produce a synergistic effect. Specifically, the pore structure on its surface provides good attachment points for the strains, thereby achieving firm attachment of the core microbial strains, so that the core microbial strains can fully play their respective roles. In addition, it can achieve physical adsorption of heavy metals by itself, and the microbial strains attached to it achieve heavy metal adsorption and reduction. The two achieve continuous adsorption and reduction of heavy metals through absorption equilibrium transfer.

[0036] (5) The composite adjuvant is to further assist the carrier and the composite bacterial agent in the adsorption of heavy metal ions. Potassium humate contains a large amount of organic acids and functional groups. Through the strong adsorption of a large amount of organic acids and functional groups, it can form a complex with heavy metal ions. In addition, it can further reduce the heavy metal ions in the soil through chelation. Furthermore, potassium humate can improve the soil structure, form a synergistic effect with the composite bacterial agent, provide a good nitrogen source for the composite bacterial agent, and promote the activity of microorganisms. Furthermore, in terms of promoting plant growth, it can effectively increase the nitrogen content in the soil. The utilization rate of elements such as phosphorus and potassium can be increased to reduce the loss of nutrients, thereby promoting better and faster growth of rice; the added potassium magnesium silicate and zinc selenite are used to supplement trace elements, among which the trace elements zinc and selenium have strong antagonistic effects with some heavy metals, such as cadmium, which can reduce the residual cadmium in rice plants and reduce the heavy metal pollution of rice plants themselves; the element magnesium can participate in the growth of rice plants and is beneficial to promoting plant growth; the element silicon cooperates with plant cells such as the xylem cells of rice to form Si-Cd precipitation, which also plays a barrier role in the transport of cadmium in rice plants;

[0037] (6) The composite microbial agent part finally selected four strains with good compatibility and good synergistic effects through compounding. Among them, Trichoderma harzianum can secrete enzymes and antibiotics and other substances to decompose the cell walls of some common pathogenic microorganisms, thereby effectively reducing plant diseases. At the same time, it exhibits a certain adsorption effect on heavy metals, that is, it first uses the complexation of surface functional groups or proteins to fix heavy metal ions, and then reduces the heavy metal ions through its own reduction reaction to achieve the removal of heavy metal ions; Bacillus thuringiensis has good resistance and adsorption to heavy metal cadmium. It uses its surface hydroxyl and C=O groups to react with heavy metal ions to achieve adsorption and fixation. At the same time, it also plays a promoting role in rice growth. It plays a positive role in the prevention and control of some diseases and insect pests, which can reduce the use of pesticides and adopt a more natural and non-toxic way to achieve disease and insect pest control; Pseudomonas aeruginosa can synthesize fluopsin C can bind copper ions to resist excessive copper. In addition, it can also release some extracellular substances to react with heavy metal ions to achieve the removal of heavy metal ions. Furthermore, in rice cultivation, Pseudomonas aeruginosa can be used as plant rhizosphere growth-promoting bacteria to secrete growth regulators to enhance the plant's defense capabilities and promote plant growth. At the same time, it can increase cadmium accumulation by increasing rice biomass, thereby reducing rice's absorption and accumulation of cadmium, thereby reducing cadmium pollution in rice; Brown ball nitrogen-fixing bacteria can convert nitrogen in the air into nitrogen that can be absorbed by plants, thereby reducing the application of nitrogen fertilizers and increasing rice yields. Further, it can assist in improving the soil environment, thereby forming a synergistic effect with other bacterial species, increasing the soil organic matter content, improving soil fertility and air permeability, and preventing soil compaction to promote the stable growth of other bacterial species. In promoting rice growth, it can increase the number of effective tillers, thereby assisting in increasing rice yields. DETAILED DESCRIPTION

[0038] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with embodiments. Several embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive:

[0039] The present application provides a composite repair agent for heavy metal contaminated soil, which is composed of the following raw materials in parts by weight: 65-75 parts of a loading carrier, 10-15 parts of a composite auxiliary agent and 15-20 parts of a composite bacterial agent;

[0040] Specifically, the load carrier is composed of the following parts by weight: 35-40 parts of rice straw, 35-40 parts of oyster shell powder, 10-20 parts of hydroxyapatite, and 10-15 parts of diatomaceous earth;

[0041] Specifically, the composite auxiliary agent is composed of the following parts by weight: 5-10 parts of potassium humate, 5-15 parts of potassium magnesium silicate, 2-5 parts of zinc selenite, and the rest is water;

[0042] Specifically, the composite bacterial agent is composed of the following bacterial species: Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa and Azotobacter chlororaphis.

[0043] The above-mentioned composite repair agent is composed of three major parts. First, the load carrier and the composite bacterial agent cooperate with the composite bacterial agent. The composite bacterial agent can cooperate to complete the absorption and fixation of free heavy metal ions, and the load carrier can provide stable adsorption sites for the composite bacterial agent to avoid the rapid loss of core bacteria species, so as to achieve long-term soil remediation; wherein, the load carrier is mainly composed of some agricultural and aquatic waste raw materials, such as rice straw and oyster shell powder. The use of waste raw materials as the main raw materials of the load carrier can realize the full utilization of waste resources, and it is also more green and environmentally friendly; the load carrier in this scheme further includes hydroxyapatite, which is easy to react with heavy metal ions, and then can show excellent heavy metal adsorption capacity, thereby improving the load carrier's own adsorption capacity for heavy metals, and at the same time, the metabolites secreted by the composite bacterial agent attached to the load carrier can also react with heavy metal ions to a certain extent, thereby achieving heavy metal adsorption. The diatomite has a large number of pores and specific surface area, which makes it have a strong adsorption capacity. The silanol (SiOH) on the surface of diatomite can be hydrolyzed in aqueous solution to form charged siloxy groups, which undergo ion exchange and surface complexation reactions with heavy metal ions. At the same time, the pore structure on its surface allows the heavy metal ions to be physically adsorbed on its surface. Furthermore, diatomite has a synergistic effect with each strain in the composite bacterial agent. Specifically, the pore structure on its surface provides a good attachment point for the strain, thereby achieving a firm attachment of the core microbial strains, so that the core microbial strains can give full play to their respective roles. In addition, it can achieve physical adsorption of heavy metals by itself, and the microbial strains attached to it achieve heavy metal adsorption and reduction. The two achieve continuous adsorption and reduction of heavy metals through absorption balance transfer.

[0044] The composite adjuvant is to further assist the carrier and the composite bacterial agent in the adsorption of heavy metal ions; potassium humate contains a large amount of organic acids and functional groups, and through the strong adsorption of a large number of organic acids and functional groups, it can form complexes with heavy metal ions; in addition, it can further reduce the heavy metal ions in the soil through chelation. Furthermore, potassium humate can improve the soil structure, form a synergistic effect with the composite bacterial agent, provide a good nitrogen source for the composite bacterial agent, and promote the activity of microorganisms; further, in terms of promoting plant growth, it can effectively increase the nitrogen and phosphorus in the soil. The utilization rate of elements such as magnesium and potassium can be increased, the loss of nutrients can be reduced, and thus the growth of rice can be promoted better and faster; the added potassium magnesium silicate and zinc selenite are used to supplement trace elements, among which the trace elements zinc and selenium have a strong antagonistic effect with some heavy metals, such as cadmium, which can reduce the residual cadmium in rice plants and reduce the heavy metal pollution of rice plants themselves; the element magnesium can participate in the growth of rice plants and is beneficial to promoting plant growth; the element silicon cooperates with plant cells such as the xylem cells of rice to form Si-Cd precipitation, which also plays a barrier role in the transport of cadmium in rice plants.

[0045] The composite microbial agent finally selected four strains with good compatibility and good synergistic effects through compounding. Among them, Trichoderma harzianum can secrete substances such as enzymes and antibiotics to decompose the cell walls of some common pathogenic microorganisms, thereby effectively reducing plant diseases. At the same time, it exhibits a certain adsorption effect on heavy metals, that is, it first uses the complexation of surface functional groups or proteins to fix heavy metal ions, and then reduces the heavy metal ions through its own reduction reaction to achieve the removal of heavy metal ions; Bacillus thuringiensis has good resistance and adsorption to heavy metal cadmium. It uses the hydroxyl and C=O groups on its surface to react with heavy metal ions to achieve adsorption and fixation. At the same time, it also promotes the growth of rice and plays a positive role in the prevention and control of some diseases and insect pests. This can reduce the use of pesticides and adopt a more natural and non-toxic way to achieve disease and insect pest control; Pseudomonas aeruginosa can synthesize fluopsin C can bind copper ions to resist excessive copper. In addition, it can also release some extracellular substances to react with heavy metal ions to achieve the removal of heavy metal ions. Furthermore, in rice cultivation, Pseudomonas aeruginosa can be used as plant rhizosphere growth-promoting bacteria to secrete growth regulators to enhance the plant's defense capabilities and promote plant growth. At the same time, it can increase cadmium accumulation by increasing rice biomass, thereby reducing rice's absorption and accumulation of cadmium, thereby reducing cadmium pollution in rice; Brown ball nitrogen-fixing bacteria can convert nitrogen in the air into nitrogen that can be absorbed by plants, thereby reducing the application of nitrogen fertilizers and increasing rice yields. Further, it can assist in improving the soil environment, thereby forming a synergistic effect with other bacterial species, increasing the soil organic matter content, improving soil fertility and air permeability, and preventing soil compaction to promote the stable growth of other bacterial species. In promoting rice growth, it can increase the number of effective tillers, thereby assisting in increasing rice yields.

[0046] In some embodiments, the load carrier is prepared by the following method:

[0047] A1. The corn stalks are crushed and mixed with hydroxyapatite. After mixing, the mixture is calcined in a nitrogen atmosphere at a temperature of 300°C for 30-35min, then the temperature is raised to 550°C for 1h, and then the temperature is raised to 700°C for 2.5h, and the first base material is obtained after cooling; the oyster shell powder is washed and crushed into small pieces, and then dried in a high-pressure tank, taken out and squeezed into powder, sieved, and then water is added to form a second base material; it can be understood that the corn stalks and hydroxyapatite are first mixed, and the carbonization of the corn stalks can be fully achieved through three-stage gradient heating and oxygen-free calcination, so that the carbonized Corn stalks form a relatively uniform pore structure, and their good pore structure can provide good attachment points for the bacteria in the subsequent composite microbial agent. By adopting a reasonable temperature increase carbonization, corn stalks can form biochar with highly active surface functional groups such as hydroxyl and carboxyl, which can adsorb heavy metal ions through chemical reactions. It can be further understood that if the calcination conditions cannot be well controlled, it will directly affect the adsorption of heavy metal ions; indirectly, it will affect the adsorption of heavy metal ions and the promotion of plant growth through the synergistic effect with the composite microbial agent.

[0048] A2. Mix the first base material, the second base material and diatomaceous earth, stir at 25-30°C and 400-450 r / min for 30-35 min; heat to 50-55°C and stir for 1 h, then vacuum filter and collect the precipitate, and dry to obtain the loaded carrier.

[0049] In one embodiment, the composite bacterial agent is prepared by the following method:

[0050] B1, culturing Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chrysogenum in liquid seed culture medium at 25°C, 30°C, 37°C, and 28°C for 24 h, respectively;

[0051] B2, the cultured bacterial solution was inoculated into LB liquid culture medium at 10% inoculation volume, and cultured under shaking conditions at 25°C, 30°C, 37°C, and 28°C until the bacterial concentration reached OD600≈2.5, and mixed evenly at any mass ratio to obtain a composite bacterial agent;

[0052] It is understandable that by culturing different bacterial strains at different temperatures, the bacterial strains can maintain a high growth rate at the optimal temperature and control the bacterial concentration at OD600≈2.5. At this concentration, it will not cause rapid consumption of nutrients. At the same time, the bacterial concentration is also maintained within a relatively high range to achieve its corresponding functions well.

[0053] In one embodiment, in step B2, the Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chlororaphis are mixed in a ratio of 2:1:2:2; it is understandable that the appropriate ratio of the compound strains can maximize the efficacy of each strain.

[0054] In one embodiment, Trichoderma harzianum is purchased from China General Microbiological Culture Collection Center with a collection number of CGMCC-3.12840;

[0055] In one embodiment, Bacillus thuringiensis is purchased from China General Microbiological Culture Collection Center with a collection number of CGMCC-1.8790;

[0056] In one embodiment, Pseudomonas aeruginosa is purchased from China General Microbiological Culture Collection Center with a collection number of CGMCC-1.10452;

[0057] In one embodiment, the brown spherical nitrogen-fixing bacteria is purchased from China General Microbiological Culture Collection Center with a collection number of CGMCC-1.492.

[0058] In one embodiment, the composite repair agent is prepared by the following method:

[0059] S1, the carrier is mixed with the culture medium and then sterilized at high temperature, cooled to room temperature, inoculated with 10% of the composite bacterial agent, and cultured at 28-30° C. for 24 hours to obtain a first intermediate solution;

[0060] S2. Dissolve potassium magnesium silicate and zinc selenite in the silicon solution to obtain a second intermediate solution. Mix the first intermediate solution, the second intermediate solution and potassium humate, stir and filter, and dry the precipitate to obtain the composite repair agent.

[0061] The present application also provides an application of the composite repair agent in rice planting, and the application method comprises the following steps:

[0062] C1. Before transplanting rice seedlings, the paddy field is ploughed and the composite repair agent is applied at a dosage of 5-10 kg / mu. Water is added to cover the soil surface with a 2-3 cm water layer. After standing for 3 days, the field is ploughed again, and then the rice seedlings are transplanted after standing for another 5 days.

[0063] It is understandable that plowing the rice field before transplanting can effectively loosen the soil, which not only increases the porosity of the soil and improves its air permeability and water permeability, but also enables the composite repair agent to be better mixed with the soil, achieve good penetration, and enable the composite repair agent to more fully realize its repair function; and the application amount is controlled at 5-10kg / mu. On the one hand, it is necessary to ensure that a sufficient amount of the composite repair agent reaches the limit of its function, and at the same time, the application cost needs to be considered. The inventor found in the test that when the application amount exceeds 10kg / mu, although it can further enhance the absorption of heavy metal ions, it is not significant. Therefore, taking into account the cost comprehensively, the composite repair agent is controlled at 5-10kg / mu; adding water, covering and standing for three days before double plowing can more fully achieve the mixing of the composite repair agent and the soil, thereby providing a good soil environment for rice transplanting.

[0064] C2. After the rice enters the tillering stage, spray the compound adjuvant at 0.5-1L / mu to cover the soil surface with a water layer of 2-3.5cm;

[0065] It is understandable that further spraying of composite auxiliary agents after rice enters the tillering stage can further supplement various trace elements and promote the growth of rice plants. At the same time, the antagonistic effect of trace elements on heavy metals can be used to further reduce the pollution of heavy metals to rice plants.

[0066] C3. After the rice enters the booting stage, apply the composite repair agent at a rate of 0.5-1kg / mu, so that the soil surface is covered with a 3.5-5cm layer of water.

[0067] It is understandable that after the rice enters the booting stage, adding a small amount of composite repair agent can improve the sustainability of heavy metal repair, and the repair effect can be improved by applying it in batches.

[0068] C4. Keep the soil surface covered with 2-3cm of water during the flowering, filling and milky stages of rice until the rice enters the waxy stage and is harvested.

[0069] In one embodiment, in step C1, the application amount of the composite repair agent is 8 kg / mu.

[0070] In one embodiment, the rice variety is Juliangyou 751.

[0071] Some specific examples are given below, and if % is mentioned, it means percentage by weight. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial sources unless otherwise specified.

[0072] Example 1

[0073] The corn stalks are crushed and mixed with hydroxyapatite, and then calcined for 30-35 minutes at 300°C in a nitrogen atmosphere, and then heated to 550°C for 1 hour, and then heated to 700°C for 2.5 hours, and then cooled to obtain a first base material; the oyster shell powder is washed and crushed into small pieces, and then dried in a high-pressure tank, taken out and squeezed into powder, sieved, and then water is added to form a second base material;

[0074] The first base material, the second base material and diatomaceous earth are mixed, and stirred at 25-30°C and 400-450r / min for 30-35min; the temperature is raised to 50-55°C and stirred for 1h, and then the precipitate is vacuum filtered and dried to obtain a loaded carrier;

[0075] Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chrysogenum were cultured in liquid seed medium at 25°C, 30°C, 37°C, and 28°C for 24 h, respectively;

[0076] The cultured bacterial liquid was inoculated into LB liquid culture medium at 10% inoculation rate, and cultured under shaking conditions at 25°C, 30°C, 37°C, and 28°C until the bacterial concentration reached OD600≈2.5, and mixed at a ratio of 2:1:2:2 to obtain a composite bacterial agent;

[0077] The carrier is mixed with the culture medium and then sterilized at high temperature. After cooling to room temperature, the composite bacterial agent is inoculated with 10%, and cultured at 28-30° C. for 24 hours to obtain a first intermediate solution; potassium magnesium silicate and zinc selenite are dissolved in the silicon solution to obtain a second intermediate solution, the first intermediate solution, the second intermediate solution and potassium humate are mixed and stirred, and then filtered, and the precipitate is dried to obtain the composite repair agent;

[0078] Among them, there are 70 parts of loading carrier, 12 parts of composite auxiliary agent and 18 parts of composite bacterial agent.

[0079] The composite repair agent prepared by the above method is applied to rice planting:

[0080] Before transplanting rice seedlings, the paddy field is plowed and the composite repair agent is applied at a dosage of 8kg / mu. Water is added to cover the soil surface with a 2-3cm water layer. After standing for 3 days, the field is plowed again, and then the rice seedlings are transplanted after standing for another 5 days.

[0081] After the rice enters the tillering stage, spray the compound adjuvant at 0.8L / mu to cover the soil surface with a water layer of 2-3.5cm;

[0082] After the rice enters the booting stage, apply the composite repair agent at a rate of 0.8kg / mu, so that the soil surface is covered with a 3.5-5cm layer of water;

[0083] During the flowering, filling and milky stages of rice, the soil surface is kept covered with a 2-3 cm layer of water until the rice enters the waxy stage and is harvested.

[0084] Among them, the rice plant variety selected was Juliangyou 751.

[0085] Example 2

[0086] This embodiment is basically the same as embodiment 1, except that the loading carrier is 65 parts, the composite auxiliary agent is 15 parts, and the composite bacterial agent is 20 parts.

[0087] Example 3

[0088] This embodiment is basically the same as embodiment 1, except that the loading carrier is 75 parts, the composite auxiliary agent is 10 parts, and the composite bacterial agent is 15 parts.

[0089] Comparative Example 1

[0090] This comparative example is basically the same as Example 1, except that the composite repair agent added in Example 1 is uniformly replaced with an organic-inorganic mixed fertilizer.

[0091] Comparative Example 2

[0092] This comparative example is basically the same as Example 1, except that no composite auxiliary agent is added in this comparative example.

[0093] Comparative Example 3

[0094] This comparative example is basically the same as Example 1, except that no composite bacterial agent is added in this comparative example.

[0095] Comparative Example 4

[0096] This comparative example is basically the same as Example 1, except that after the rice enters the tillering stage, the composite adjuvant is no longer sprayed, but the composite adjuvant is sprayed after plowing before rice transplanting.

[0097] Comparative Example 5

[0098] This comparative example is basically the same as Example 1, except that the composite repair agent is no longer applied after the rice enters the booting stage, but is applied together after turning over and plowing before rice transplanting.

[0099] Comparative Example 6

[0100] This comparative example is basically the same as Example 1, except that the rice variety used is Meixiangzhan.

[0101] Comparative Example 7

[0102] This comparative example is basically the same as Example 1, except that the rice variety used is Shengyouhuangzhan.

[0103] The test site was selected in a plot of land in Huizhou City, Guangdong Province. The soil was slightly contaminated with cadmium and partially contaminated with arsenic.

[0104] The above embodiments and comparative examples were tested as follows:

[0105] 1. Analysis of metal content in polished rice;

[0106] 2. Analysis of soil heavy metal removal rate;

[0107] 3. Analysis of rice yield.

[0108] Table 1: Analysis of metal content in polished rice

[0109]

[0110]

[0111] Table 2: Analysis of soil heavy metal removal rate

[0112] deal with Cadmium removal rate (%) Arsenic removal rate (%) Chromium removal rate (%) Example 1 90.2 88.6 86.3 Example 2 87.2 84.5 83.7 Example 3 86.3 83.9 82.9 Comparative Example 1 3.6 3.0 3.2 Comparative Example 2 64.8 63.3 62.9 Comparative Example 3 61.9 60.7 60.2 Comparative Example 4 75.9 74.7 72.6 Comparative Example 5 74.5 73.1 71.4

[0113] Table 3: Rice yield analysis

[0114]

[0115]

[0116] The present application provides a composite repair agent for heavy metal contaminated soil and its application in rice planting, which has at least the following beneficial effects:

[0117] (1) The composite repair agent is composed of three major components, which work synergistically with each other. The load carrier and the composite bacterial agent work together to form a composite bacterial agent. The composite bacterial agent can achieve the absorption and fixation of free heavy metal ions, and the load carrier can provide a stable adsorption point for the composite bacterial agent to avoid the rapid loss of core bacteria, so as to achieve long-term soil remediation. The composite auxiliary agent cooperates to provide trace elements, forms a synergistic effect with the soil body, and provides a good basic environment for the growth of microorganisms.

[0118] (2) The raw material source is green and environmentally friendly. The load carrier is mainly composed of some agricultural and aquatic waste materials, such as rice straw and oyster shell powder. Using waste materials as the main raw material of the load carrier can make full use of waste resources and is also more green and environmentally friendly;

[0119] (3) The load carrier in this scheme further includes hydroxyapatite, which is easy to react with heavy metal ions to form a complex, thereby showing a relatively excellent heavy metal adsorption capacity, and improving the load carrier's own heavy metal adsorption capacity. At the same time, the metabolites secreted by the composite bacterial agent attached to the load carrier can also react with heavy metal ions to a certain extent, thereby achieving the adsorption of heavy metal ions; further, the rich phosphorus element can also provide assistance for plant growth, which is beneficial to reduce diseases and increase rice yields;

[0120] (4) Diatomaceous earth has a large number of pores and specific surface area, which makes it have a strong adsorption capacity. The silanol (SiOH) on the surface of diatomaceous earth can be hydrolyzed in aqueous solution to form charged siloxy groups. These groups undergo ion exchange and surface complexation reactions with heavy metal ions. At the same time, the pore structure on its surface allows heavy metal ions to be physically adsorbed on its surface. Furthermore, diatomaceous earth and the various strains in the composite bacterial agent produce a synergistic effect. Specifically, the pore structure on its surface provides good attachment points for the strains, thereby achieving firm attachment of the core microbial strains, so that the core microbial strains can fully play their respective roles. In addition, it can achieve physical adsorption of heavy metals by itself, and the microbial strains attached to it achieve heavy metal adsorption and reduction. The two achieve continuous adsorption and reduction of heavy metals through absorption equilibrium transfer.

[0121] (5) The composite adjuvant is to further assist the carrier and the composite bacterial agent in the adsorption of heavy metal ions. Potassium humate contains a large amount of organic acids and functional groups. Through the strong adsorption of a large amount of organic acids and functional groups, it can form a complex with heavy metal ions. In addition, it can further reduce the heavy metal ions in the soil through chelation. Furthermore, potassium humate can improve the soil structure, form a synergistic effect with the composite bacterial agent, provide a good nitrogen source for the composite bacterial agent, and promote the activity of microorganisms. Furthermore, in terms of promoting plant growth, it can effectively increase the nitrogen content in the soil. The utilization rate of elements such as phosphorus and potassium can be increased to reduce the loss of nutrients, thereby promoting better and faster growth of rice; the added potassium magnesium silicate and zinc selenite are used to supplement trace elements, among which the trace elements zinc and selenium have strong antagonistic effects with some heavy metals, such as cadmium, which can reduce the residual cadmium in rice plants and reduce the heavy metal pollution of rice plants themselves; the element magnesium can participate in the growth of rice plants and is beneficial to promoting plant growth; the element silicon cooperates with plant cells such as the xylem cells of rice to form Si-Cd precipitation, which also plays a barrier role in the transport of cadmium in rice plants;

[0122] (6) The composite microbial agent part finally selected four strains with good compatibility and good synergistic effects through compounding. Among them, Trichoderma harzianum can secrete enzymes and antibiotics and other substances to decompose the cell walls of some common pathogenic microorganisms, thereby effectively reducing plant diseases. At the same time, it exhibits a certain adsorption effect on heavy metals, that is, it first uses the complexation of surface functional groups or proteins to fix heavy metal ions, and then reduces the heavy metal ions through its own reduction reaction to achieve the removal of heavy metal ions; Bacillus thuringiensis has good resistance and adsorption to heavy metal cadmium. It uses its surface hydroxyl and C=O groups to react with heavy metal ions to achieve adsorption and fixation. At the same time, it also plays a promoting role in rice growth. It plays a positive role in the prevention and control of some diseases and insect pests, which can reduce the use of pesticides and adopt a more natural and non-toxic way to achieve disease and insect pest control; Pseudomonas aeruginosa can synthesize fluopsin C can bind copper ions to resist excessive copper. In addition, it can also release some extracellular substances to react with heavy metal ions to achieve the removal of heavy metal ions. Furthermore, in rice cultivation, Pseudomonas aeruginosa can be used as plant rhizosphere growth-promoting bacteria to secrete growth regulators to enhance the plant's defense capabilities and promote plant growth. At the same time, it can increase cadmium accumulation by increasing rice biomass, thereby reducing rice's absorption and accumulation of cadmium, thereby reducing cadmium pollution in rice; Brown ball nitrogen-fixing bacteria can convert nitrogen in the air into nitrogen that can be absorbed by plants, thereby reducing the application of nitrogen fertilizers and increasing rice yields. Further, it can assist in improving the soil environment, thereby forming a synergistic effect with other bacterial species, increasing the soil organic matter content, improving soil fertility and air permeability, and preventing soil compaction to promote the stable growth of other bacterial species. In promoting rice growth, it can increase the number of effective tillers, thereby assisting in increasing rice yields.

[0123] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0124] The above description is only a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application are within the scope of the technical solution of the present application.

Claims

1. A composite remediation agent for heavy metal contaminated soil, characterized in that: The method is composed of the following raw materials in parts by weight: 65-75 parts of a loading carrier, 10-15 parts of a composite auxiliary agent and 15-20 parts of a composite bacterial agent; The load carrier is composed of the following parts by weight: 35-40 parts of rice straw, 35-40 parts of oyster shell powder, 10-20 parts of hydroxyapatite, and 10-15 parts of diatomaceous earth; The composite auxiliary agent is composed of the following parts by weight: 5-10 parts of potassium humate, 5-15 parts of potassium magnesium silicate, 2-5 parts of zinc selenite, and the rest is water; The composite bacterial agent is composed of the following bacterial species: Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa and Nitrogen-fixing Bacterium chlororosum.

2. The composite remediation agent for heavy metal contaminated soil according to claim 1, characterized in that: The load carrier is prepared by the following method: A1. The corn stalks are crushed and mixed with hydroxyapatite, and then calcined for 30-35 min at 300° C. in a nitrogen atmosphere, and then heated to 550° C. for 1 h, and then heated to 700° C. for 2.5 h, and then cooled to obtain a first base material; the oyster shell powder is washed and crushed into small pieces, and then dried in a high-pressure tank, taken out and squeezed into powder, sieved, and then water is added to form a second base material; A2. Mix the first base material, the second base material and diatomaceous earth, stir at 25-30°C and 400-450 r / min for 30-35 min; heat to 50-55°C and stir for 1 h, then vacuum filter and collect the precipitate, and dry to obtain the loaded carrier.

3. The composite remediation agent for heavy metal contaminated soil according to claim 1, characterized in that: The composite bacterial agent is prepared by the following method: B1, culturing Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chrysogenum in liquid seed culture medium at 25°C, 30°C, 37°C, and 28°C for 24 h, respectively; B2. The cultured bacterial liquid was inoculated into LB liquid culture medium at 10% inoculation rate, and cultured under shaking conditions of 25°C, 30°C, 37°C, and 28°C until the bacterial concentration reached OD600≈2.

5. The mixture was evenly mixed at any mass ratio to obtain a composite bacterial agent.

4. The composite remediation agent for heavy metal contaminated soil according to claim 3, characterized in that: In step B2, the Trichoderma harzianum, Bacillus thuringiensis, Pseudomonas aeruginosa, and Azotobacter chlororaphis are mixed in a ratio of 2:1:2:

2.

5. The composite remediation agent for heavy metal contaminated soil according to claim 3, characterized in that: The Trichoderma harzianum was purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-3.12840; The Bacillus thuringiensis was purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-1.8790; The Pseudomonas aeruginosa was purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-1.10452; The brown spherical nitrogen-fixing bacteria were purchased from China General Microbiological Culture Collection Center with the collection number of CGMCC-1.

492.

6. The composite remediation agent for heavy metal contaminated soil according to any one of claims 1 to 5, characterized in that: The composite repair agent is prepared by the following method: S1, the carrier is mixed with the culture medium and then sterilized at high temperature, cooled to room temperature, inoculated with 10% of the composite bacterial agent, and cultured at 28-30° C. for 24 hours to obtain a first intermediate solution; S2. Dissolve potassium magnesium silicate and zinc selenite in the silicon solution to obtain a second intermediate solution. Mix the first intermediate solution, the second intermediate solution and potassium humate, stir and filter, and dry the precipitate to obtain the composite repair agent.

7. Application of the composite repair agent according to any one of claims 1 to 6 in rice planting: the application method comprises the following steps: C1. Before transplanting rice seedlings, the paddy field is plowed and the composite repair agent is applied at a dosage of 5-10 kg / mu. Water is added to cover the soil surface with a 2-3 cm water layer. After standing for 3 days, the field is plowed again, and then the rice seedlings are transplanted after standing for another 5 days. C2. After the rice enters the tillering stage, spray the compound adjuvant at 0.5-1L / mu to cover the soil surface with a water layer of 2-3.5cm; C3. After the rice enters the booting stage, apply the composite repair agent at a rate of 0.5-1kg / mu, so that the soil surface is covered with a 3.5-5cm layer of water. C4. Keep the soil surface covered with a 2-3 cm layer of water during the flowering, filling and milky stages of rice until the rice enters the waxy stage and is harvested.

8. Use of the composite repair agent according to claim 7 in rice planting: in step C1, the application amount of the composite repair agent is 8 kg / mu.

9. The use of the composite repair agent in rice planting according to claim 7, characterized in that: The rice variety is Juliangyou 751.

10. The use of the composite repair agent in rice planting according to claim 9, characterized in that: The application is to reduce the cadmium content in rice.

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